FRIDAY, March 29 (HealthDay News) -- Drug-resistant bacteria that cause lung infections in people with cystic fibrosis can be passed indirectly from person to person, a new study finds.

Between 3 percent and 10 percent of cystic fibrosis patients in the United States and Europe are infected with multi-drug resistant Mycobacterium abscessus, and the numbers are rising. The difficult-to-treat infection causes progressive lung damage.

In this study, researchers conducted DNA tracking of a multi-drug resistant M. abscessus outbreak that occurred among 31 cystic fibrosis patients at a British treatment center between 2007 and 2011.

Despite tight infection-control measures, patient-to-patient transmission was common, according to the study, published online March 29 in the journal The Lancet.

The researchers were unable to pinpoint the exact method of cross-infection between the patients. They said it likely occurred through contamination of things such as hair, clothing and bedding, or when bacteria were released into the air during procedures such as lung function tests.

The findings will have a major effect on how cystic fibrosis patients are cared for in hospitals and raise questions about the effectiveness of current infection-control measures and the risk of multi-drug resistant M. abscessus cross infection in other groups of patients, said Dr. Andres Floto, of the University of Cambridge, and colleagues.